What is it about?
Energy transfer problem in extended aggregates is multidimensional, involving multiple electronic states and multiple vibrational modes, with limited to no knowledge of which vibrational motions drive energy transfer against vibrational motions which play no role in the process. We derive effective normal modes to identify reaction coordinates for energy transfer in extended molecular aggregates. These normal modes represent effective slices on the multidimensional vibrational space, motions along which enhance energy transfer. We exemplify our approach to identify a novel design principle of trap-mediated energy transport. Uncoupled donor-acceptor sites do not exchange energy. A trap site will receive all the excitation from the donor without transferring it to the acceptor. We show that by modulating vibrational motions along specific directions, the `trap' can be converted to a `shuttle' for promoting donor-acceptor energy transfer, even if donor and acceptor are uncoupled.
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Why is it important?
Role of vibrational motions in driving photochemistry is a subject of active investigation. Inducing specific vibrational motions can drive photoinduced charge transfer, interfacial charge separation and electronic phase transitions, motivating a need for identifying physically relevant vibrational motions which maximally promote electronic dynamics against mere spectator modes, in order to potentially control energy and charge transport by modulating vibronic interactions. Our approach to multidimensional energy transfer problem reduces the problem into one-dimensional problems along these effective vibrational normal modes. By reducing the problem into one-dimensional problems, we can identify, in a physically meaningful way, which normal modes maximally promote mixing of vibrational and electronic motions to drive energy transfer, without having to make oversimplifying approximations which do not fully capture the role of vibrations in promoting electronic energy transfer.
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This page is a summary of: Effective normal modes identify vibrational motions which maximally promote vibronic mixing in excitonically coupled aggregates, The Journal of Chemical Physics, March 2021, American Institute of Physics, DOI: 10.1063/5.0037759.
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